Turn Monitor off, use Keyboard LEDs

There are some tools which allow to get information from your computer without using the monitor:

bl : Blink Keyboard LEDs

blinkd : "Blinks keyboard LEDs for an answering
machine or fax machine. Blinkd is a client/server pair, that lets the
keyboard LEDs blink, indicating things like the number of incoming voice
calls in the voice box or incoming faxes in the spool."

mailleds : Shows new mails with the keyboard LEDs,
mailleds is a quiet, unobtrusive way to signify that
you have new mail: a user daemon to blink LEDs when there is new mail.

tleds : Blinks keyboard LEDs indicating TX and RX network
packets. They blink Scroll-Lock LED when a network packet leaves the
machine, and Num-Lock LED when one is received.

ledcontrol:
is a program that allows you to show different information on the
normally-unused LEDs on your keyboard. You can configure it to show virtually
any true/false condition accessible or indicate an arbitrary number. The
monitoring is by default done by shell scripts to allow for maximal
configurability.